Stuttering, also known as stammering, is a common speech disorder known since antiquity, affecting all populations and language groups. Stuttering is a disorder of unknown etiology characterized by repetitions, prolongations and interruptions in the flow of speech. Although the underlying causes of stuttering are unknown, substantial evidence from twin studies, adoption studies and family studies support genetic contributions to the etiology of the disorder. Such data have motivated a number of genetic linkage studies that have produced evidence for linkage at numerous loci across the genome (Riaz et al., Am. J. Hum. Genet., 76:647-651 (2005); Wittke-Thompson et al., J. Fluency Disord. 32:33-50 (2007); Suresh et al., Am. J. Hum. Genet., 78:554-563 (2006)). The most statistically significant linkage has been reported on the long arm of chromosome 12, based on the study of a group of consanguineous families in Pakistan (Riaz et al.). However, numerous genome-wide linkage scans performed in stuttering families have failed to identify robust linkage signals (Shugart et al., Suresh et al.). The lack of understanding of the etiology of stuttering has, until now, limited the ability to diagnose and treat this disorder.